218 GENERAL VIEW OF THE FUNCTIONS. 



from those of Physics and Chemistry, as these are from each other. It is to 

 such phenomena, that the name of Vital is properly restricted ; the forces 

 from whose operation we assume them to result, are termed vital forces ; and 

 the properties, which we must attribute to the substances exerting those forces, 

 are termed vital properties. Thus we say that the contraction of Muscle is 

 a Vital phenomenon ; because its character and conditions appear to be to- 

 tally distinct from those of Chemical or Physical phenomena. The act is 

 the manifestation of a certain Force ; the possession of which is peculiar to 

 the muscular structure, and which is named the Contractile force. Further, 

 that force may remain dormant (as it were) in the muscular structure ; not 

 manifesting itself for a great length of time, and yet resting capable of being 

 called into opera ion at any moment. This dormant force is termed a Pro- 

 perty ; thus we regard it as the essential peculiarity of living muscular tissue, 

 that it possesses the vital property of Contractility. Or, to reverse the order, 

 the Muscle is said to possess the property of Contractility ; the property, 

 called into operation by the appropriate stimulus, gives rise to the Contractile 

 force ; and the force produces, if its operation be unopposed, the act of Con- 

 traction. 



257. These distinctions, though apparently verbal only, are of importance 

 in leading us to the correct method of investigating Vital Phenomena, and of 

 comparing them with those of the Inorganic world. It is now almost uni- 

 versally admitted by intelligent Physiologists, that we gain nothing by the 

 assumption of some general controlling agency, or Vital Principle, distinct 

 from the organized structure itself; and that the Laws of Life are nothing else 

 than general expressions of the conditions under which Vital operations take 

 place, expressions analogous to those which constitute the laws of Physics 

 or Chemistry, and to be arrived at in the same manner, namely, by the col- 

 lection and comparison of phenomena. The difficulty of thus generalising in 

 Physiology results merely from the complex nature of the phenomena, and 

 the consequent difficulty of precisely determining their conditions. We have 

 as much ground for believing in the fixity and constancy of Physiological 

 phenomena, when the causes and conditions are the same, as we have in those 

 of any other department of science ; and the apparent uncertainty of the 

 actions of the living body, results merely from the influence of differences in 

 those conditions, so trivial in appearance as frequently to elude observation, 

 and yet sufficiently powerful in reality to produce an entire change in the 

 result. 



258. All Vital phenomena are dependent upon at least two sets of condi- 

 tions; an Organized structure, possessed of peculiar properties ; and certain 

 Stimuli, by which these properties are called into action. Thus, to revert to 

 the example just cited, the Contraction of a Muscle is due to the inherent 

 Contractility of the Muscular tissue, called into operation by the stimulus of 

 innervation ; other conditions, as a certain elevated temperature, a supply of 

 oxygen, &c., being at the same time requisite. The Microscopical and 

 Chemical researches of recent years, have given increased stability to the 

 position, that the peculiar properties, which we term Vital, are dependent 

 upon those peculiar modes of combination and aggregation of the elementary 

 particles, which are characteristic of Organized structures. We have no evi- 

 dence of the existence of Vital properties in any other form of matter than 

 that which we term Organized; whilst, on the other hand, we have no reason 

 to believe that Organized matter can possess its normal constitution, and be 

 placed in the requisite conditions, without exhibiting Vital Actions. The 

 advance of Pathological science renders it every day more probable (indeed, 

 the probability may now be said to amount almost to positive certainty), that 

 derangement injunction, in other words, an imperfect or irregular action, 



